4376fbd793
Summary: We use this `dyn_ptr` argument in Clang/OpenMP to handle the `KernelLaunchEnvironment`. This is a per-kernel argument used to share some information. Currenetly, it's prepended to the argument list and we generate storage for it in the runtime. This is bad for a few reasons: 1. It changes the ABI by shifting user arguments 2. It cannot be trivially be left uninitialized if unused 3. The runtime must allocate its own memory for it This PR changes it to be appended instead. Additionally, space for this is always emitted. This means the OMPIRBuilder itself will provide the storage, we simply need to populate it in the runtime if it is used. This means that if it's unused we don't always pay the cost and it's easier for non-OpenMP users to ignore it. Backward compatibility is maintained by auto-upgrading the kernel arguments. In `libomptarget` we completely allocate a new buffer to store this in the new format. The plugins still need to respect the old ABI of the called device object, so we simply rotate it if it's the old version.
The LLVM/Offload Subproject
The Offload subproject aims at providing tooling, runtimes, and APIs that allow users to execute code on accelerators or other "co-processors" that may or may not match the architecture of their "host". In the long run, all kinds of targets are in scope of this effort, including but not limited to: CPUs, GPUs, FPGAs, AI/ML accelerators, distributed resources, etc.
For OpenMP offload users, the project is ready and fully usable. The final API design is still under development. More content will show up here and on our webpage soon. In the meantime, people are encouraged to participate in our meetings (see below) and check our development board as well as the discussions on Discourse.
Meetings
Every second Wednesday, 7:00 - 8:00am PT, starting Jan 24, 2024. Alternates with the OpenMP in LLVM meeting. invite.ics Meeting Minutes and Agenda